The natural history and biology of the recently erected family Viridasiidae is virtually unknown, although members of Viridasius Simon, 1889 are frequently used in cladistical or toxicological studies. Therefore, we report on laboratory observations made of the feeding and mating behavior and describe the egg-sac of a species tentatively assigned to Viridasius. The spiders were mostly nocturnal and built a large, silken retreat for molting. Females built pendulum-like egg sacs consisting of a silken, string-like stalk and an oval repository. The egg-sacs were covered actively with substrate by the female. Our observations corroborate the positioning of the Viridasiidae outside of the Ctenidae, because pendulous and camouflaged egg-sacs are not known from any ctenid species to date.